Grease the bottoms and about 1/2 inch up the sides of two 8x4x2-inch loaf pans. Set the pans aside.
In a medium mixing bowl, stir together flour, cinnamon, salt, baking soda, and baking powder.
In a large mixing bowl, beat eggs. Stir in sugar, oil, and honey. Stir in apple, zucchini, and vanilla. Fold in the flour mixture until just moistened (don't overmix). Fold in the nuts, if you like. Spoon the batter into the prepared pans.
Bake in a 325 degree F oven for 50 to 55 minutes or until a wooden toothpick inserted near center of each loaf comes out clean. Cool loaves in the pans on a wire rack for 10 minutes. Loosen the edges and remove the loaves from pans. Cool completely on the wire racks. Makes 2 loaves, 16 servings per loaf.